We are (1) studying the efficacy and remission rate of narrowband UVB in the treatment of psoriasis. Previous studies show a satisfactory response in 80% of the patients treated. 38% of patients remained in remission for one year. (2) investigating the mechanism of action of narrowband UVB phototherapy. (3) Comparing the efficacy and remission rate of narrowband UVB with conventional UVB. Conventional UVB yields a 70% satisfactory response rate with only 5% of patients remaining in remission for one year.